How Epson inkjets work

How Epson Inkjet Printers Work

The details about the the operation of Epson inkjets are mostly company confidential, and therefore consumers are often puzzled by the strange behavior of their devices. This article gives my opinion on the subject, which can explain several weird phenomenon related to this machine. This is not intended to be a book of revelations, my aim is to gather the bits of information provided around the web to provide at least plausible explanation on the subject. I focus on the printing mechanism, ink consumption, and ink cartridges, trying to explain why these printers are prone to waste massive amounts of ink or die.

Important update!
I recommend all Epson users to try SSC Service Utility for coping with Epson.

General

Picture 1. An illustration of the structure of the ink container and the print head, displaying the ink channel (based on reference #1)

Epson printers contain several features that are unique among inkjet manufacturers. Maybe the most essential difference is in the way ink is transferred to paper. Epson solely relies on piezoelectronic driven printhead that drives the ink through the microscopic nozzles. Maybe this technique is more expensive (and accurate?) than the competing technologies, because it is implemented outside the ink cartridge as a fixed part of the printhead. This means that if your printhead gets stuck, you're having a major problem, because the printhead cannot be replaced easily. In normal conditions, the printer always tries to keep the ink channel and nozzles full of fresh ink, so it would not dry out, or even worse, rust. There are several ways for the printer do this. First is use to use ink, constantly. If you try to print just 'black and white' you'll always waste a little bit of the others colours just in order to keep the ink running. For the same reason, Epson instructs all printer owners to use their printer once a month, otherwise it can dry out. Additionally, it is necessary that you turn off the printer by pressing the power button, not just pulling the plug. This is because the printhead has a special parking position that allows it to 'sit still' for several weeks without drying. The third thing is the automatic maintenance cycle, which does a quick print-head cleaning every now and then. I have a few words about this feature in the next paragraph.

Print-head cleaning

As said, the biggest and inevitable problem associated with the fixed, external printhead is that it can get clogged. Sometimes, which appears to be random for an uninformed observer, the printer makes a fuzzing sound for a while when turning or finishing printing, similar sound as when it loads paper. This indicates an automatic cleaning cycle in which a vacuum pump sucks some amount ink out of all containers. The pump is driven by the motor as the paper feeder, which is the reason for the noise. There is no way you can prevent this, but this effect can be minimized by turning on the printer only when you're going to print and print several documents at a time. If you don't feel comfortable with this, consider getting a laser printer instead. If heads do get clogged, you will have to use the Head cleaning function, which is the greatest 'bye-bye-ink' operation of all. It must be initiated by the user, as the printer has no way of knowing whether it is succesfully printing or not. It can be started from the printer software (driver dialog, Head cleaning) or alternatively by a button combination from the unit itself, see your manual. What is not mentioned in the manual is the fact that the cleaning process has two or three levels of duty, initial, medium and heavy (depending on printer/source of information). After running all levels, you should not push your printer further, because it will just waste ink from those color cartridges that are still running because the cleaning cannot be restricted to any single color (to my best knowledge) .

The amount of ink wasted seems therefore considerable, and I would have not believed the printer to be a such ink drinker before I disassembled my printer. And found out where all my precious ink had gone. See for yourselves what happens during and after the cleaning process:

Picture 2. During the printhead cleaning ink is forcefully sucked through the nozzles to a hose (top and middle) which leads wasted ink to absorping pads located inside the printer (bottom)

Like laser units, Epson inkjets are equipped with absorbing cotton (etc.) pads laid on the bottom of the unit to capture all leaking ink. Some sources indicate that the printer also keeps a record of all cleaning, printing and loading operations to approximate when the waste ink pads have reached their limits and after that, refuses to print before maintenance. Some people have written a software to reset this counter, so you should be able to find it with Google.

Ink cartridges

Epson ink cartridges are quite simple. They have no real electronics, from the image below (picture 3) you can see that they are just plastic containers that have a small chip (pic. 3, black arrow) attached to them. The chip identifies the cartridge type and is used for approximating the remaining ink level, in a very conservative way. The chip is the reason underlying the 2006 Epson settlement, which Epson lost.

Some time ago, I tried to Google to find out if Epson provides half-empty (or half-filled, starter or moderate use) bundle cartridges with their printers and is there some difference between 'genuine Epson' and third-party (pirated, in Epson's opinion) inks. In reply to the former question, it turned out that no agreement was found, some sources claimed one, some the other, with a varying degree of confidence. In the case of HP printers, this issue is clear. HP has identifiable product numbers for these 'starter' cartridges.

So, to solve this issue regarding Epson, I decided to experiment myself. I disassembled an original cartridge that was provided with my Epson CX3650 multipurpose printer (a european model, same cartridge is used in C64/68 US model) and compared it to a third-party cartridge. The Epson cartridge had been removed from the printer about a year ago and was empty as it can be, the third-party product was just recently discarded. The difference was shown above in the picture 3.

Picture 3. The original (onright, yellow) and a third party cartridge (on left, magenta).

So, some things pop out. First, it is clearly visible that Epson cartridge has never been full (gray arrow). There are compartments that are not dyed with yellow ink, whereas in the third-party cartridge, you can clearly see stains all over the unit. Another discrepancy concerns the amount of dry ink, although both containers are practically empty, the genuine is still 'fresh' inside even though it has been on my bookshelf for a year! The third-party cartridge has already began to dry up internally. This might have something to do with the spring-loaded 'button' found in the bottom of genuine cartridge, non-existent in the third-party product. This button gets loaded when the cartridge is in place and my guess is that it is normally used to make the container more air tight. In a recent post to Macintouch, Mark Barnes reported that bundled cartridges weight less than genuine replacements, which backs up this claim.

So, you might conclude that genuine Epson cartridges are better protected against 'natural' drying out, whereas third-party products may use whatever mechanism (if any) to seal themselves. This might be one explanation for the often reported but seldom explained phenomenon of clogged printheads due to the use of 'pirate inks'. But I suspect that there's more. While the third-party products claim that the results will match exactly those of original ink, in terms of color parameters, it is another issue whether the colors last as long as original or are the inks harmful to your printheads. The increased clogging might have something to do with formula of the ink, my guess is that genuine inks contains ingredients specifically intended to keep the printheads working, maybe a some solvent that slows down the drying process just the right amount. As a conclusion, you can use pirate stuff if you print a lot, because you'll changing the cartridges so often your printer won't get clogged. If you seldom print anything, then go for the genuine products, it will a worthy investment, because you must remember that every time you are forced to the Head cleaning process, a huge amount of ink is wasted and small savings can become considerable losses and you risk completely 'killing' your printer.